Polyester resins containing a hydroxypyridine



United States Patent 3,548,029 POLYESTER RESINS CONTAINING AHYDROXYPYRIDINE Eldon E. Stahly, Ellicott City, and Edwin W. Lard,Bowie, Md., assignors to W. R. Grace & (30., New York, N.Y., acorporation of Connecticut No Drawing. Filed Dec. 10, 1968, Ser. No.782,708 Int. Cl. C08f 21/02 US. Cl. 260-864 Claims ABSTRACT OF THEDISCLOSURE Hydroxypyrdines are added to uncured polyester resin systemsto prevent gelation of those systems when they are stored at roomtemperature or at elevated temperatures for periods of time in excess ofthree years. Between 0.5 and 1.0 mole percent of the hydroxypyridines isadded to the uncured polyester systems.

The invention herein described was made in the course of or under acontract or subcontract thereunder, wlth the Department of the AirForce, Department of Defense.

BACKGROUND OF THE INVENTION Objectives of the invention It is an objectof this invention to prevent the gelation of admixtures of uncuredpolyester components during prolonged periods of storage at roomtemperatures and at elevated temperatures. Other objectives will beobvious.

Prior art Conventional inhibitors are added in amounts up to about0.0005 mole percent to preserve polyester resins in the liquidunpolymerized stage at temperatures of 77 F. and higher, but the maximumshelf life is about six months.

BROAD DESCRIPTION OF THE INVENTION This invention, broadly, involves amethod of prolonging the useful life of uncured polyester resincompositions by preventing the gelling and cross-linking thereof duringstorage, normally at ambient temperatures. That result can be achievedby incorporation between about 0.5 and about 1.0 mole percent of thenovel inhibitors of this invention into uncured polyester resincompositions. Those stabilized uncured polyester resin compositions canbe stored and maintained in useful unpolymerized fluid form for periodsup to 3 years or more at 70 C. and for periods from 3 to 30 years at 25to 50 C. Of course, storage temperatures below C. and as high at 135 C.can be used.

The novel process of this invention for prolonging the storage ofuncured polyester resin compositions by preventing the gelling of thosepolyester resin compositions includes: admixing at least one inhibitorhaving the formula:

N RsT R4 wherein: R is H or OH; R is H or OH; R is H or OH; R; is H orOH; and R is H or OH; provided at least one of R R R R and 5 is OH; andan uncured polyester resin composition which includes at least onemonomer, wherein said inhibitor is present in an amount between about0.05 and about 1.0 mole percent based upon the amount of said monomer ormonomers; and storing said polyester resin composition.

3,548,029 Patented Dec. 15, 1970 Quantities expressed herein as molepercent are defined as moles per hundred grams of polyester resinformulation.

The examples below bear out the fact that conventional amounts.(0.00001to 0.001 mole percent) of inhibitors (also termed a free radicalscavenging type of crosslinking inhibitor) were found inadequate forstorage for periods of time longer than six months. Amounts larger thannormally used by the art (up to 1 mole percent) were tested forcomparison with the new stable formulations of this invention, however,the conventional stabilizers were found very inferior even at those highconcentrations. A one-thousand fold increase in the conventionalconcentration (0.001 weight percent) of those additives imparts lessthan a one year shelf-life increase to the uncured polyester resincompositions at 50 C.

Preferably, the smallest amount of inhibitor found to be effective forstorage stability is used so that the composition can be easily curedafter the storage period.

This invention also includes the addition of the above said inhibitorswhen combined with (i.e., dissolved in or admixed with) isopropanol tothe uncured polyester resin compositions. The resultant stabilizedcompositions also have shelf-lives in excess of three years at preferredtemperatures below 15 C. and about 70 C. Of course, storage temperaturesbelow 15 C. and as high as C. can be used. The isopropanol is stronglysynergistic, allowing less than 0.5 mole percent of the novel inhibitorsto be dissolved in or admixed with between about 0.1 and about 3.5 molepercent isopropanol.

This invention further includes the uncured polyester resln compositionsincluding the inhibitor, or inhibitor and isopropanol, in the abovestat-ed amounts.

The stabilized uncured polyester resin compositions of this inventioncan be cured and crosslinked to form strong laminates, resin compositesand other cured resinous materials.

DETAILED DESCRIPTION OF THE INVENTION As used within the scope of thisinvention, an inhibitor is a material whose primary function is toprevent or retard internal polymerization of the polyester constituentof the resinous composition. An alternative term for an inhibitor, asused herein, is the term stabilizer (which is the term moreconventionally used by the art).

1 Specific examples of useful inhibitors are given as folows:

(a) 2-hydroxypyridine (HOC H N) which is also termed 2-pyridol,2(1)-pyridone and a-pyridone. It is soluble in water, ethanol and ether.Its structural formula is:

(b) 2,5-dihydroxypyridine, which has the following structural formula:

() 3-hydroxypyridine, which has the following structural formula:

H-(N\H I-I- \J 0 1r (d) 4-hydroxypyridine can be prepared by thedecarboxylation of chelidamic acid. It has the following structuralformula:

N l T H H \I/ 011 (e) 2,3-dihydroxypyridine which is also termed 2,3-pyridinediol. It has the following structural formula:

N T F H -OH and (f) 2,4-dihydroxypyridine, which has the followingstructural formula:

where k=rate of crosslinking of the resin at temperature T (K.), Eenergy of activation in KcaL/mole and R=1.987 cal. The rates ofcrosslinking (i.e., gelling) of polyester resin formulations of Examples1 through 5 when plotted on semi-log paper (log k vs. 1/ T) fall on astraight line for the temperature range 70 to 150 C. (158 to 302 F.).This straight-line relationship establishes the fact that the mechanismof the gelling reaction does not change over the temperature range ofinterest, and the slope of the line=-E/2.303R, and E, the activationenergy of the gelation, can be calculated for each resin. It is possibleto simplify extrapolation of the storage life at elevated temperaturesby a route which bypasses calculation of the reaction rate. The changein viscosity which occurs in the crosslinking and conversion of thefluid polyester into a non-fiowable gel is substantially constant foreach particular polyester formulation. Therefore, the rate ofcrosslinking expressed in terms of rate of change of viscosity (i.e., Aviscosity/ time) becomes C/time where C is constant. When log 1/t (time)is plotted against 1/ T K., a line is obtained having a slope identicalwith that of the line represented by l/T K. versus log k. It isconvenient to plot the colog of l/t or log (time) itself and a line ofthe same slope but of opopsite sign is obtained (t=tirne for gelatlon tooccur). Extrapolation of the straight line obtained from log 1 (time togel) versus l/T K.) can be extrapolated to any l/T value required. Theuse of accelerated storage tests based on this use of highertemperatures, enables a fast laboratory determination of whether or notthe inhibitors prevent setting of polyester resins prior to combinationwith a catalyst curing system for end use applications.

The preferred temperature range for the storage of the stabilizeduncured polyester resin compositions is about 15 to about 70 C.Temperatures below 15 C. are not ordinarily used because of the costs ofmaintaining those temperatures over long periods of time. Temperaturesas high as C. to C. are useful; but the storage life is decreased fromthose obtained when the preferred temperature ranges are utilized.

Various useful polyester resin compositions are given in the followingparagraphs.

The preferred unsaturated polymerizable mixtures to be cured by theprocess of this invention are conventional classes of resins known inthe prior art. The most preferred polyester resins are prepared by theesterification of alpha, beta-unsaturated polybasic acids, and dihydricalcohols. Certain compounds of this type may be indicated generically asfollows: M-GMGMG where, M represents an unsaturated dibasic acid residueand -G represents a dihydric alcohol residue. Modifying dibasic acidsmay also be used in the polyester resin compositions. Representativedihydric alcohol and unsaturated polybasic acids are shown below.

In preparing unsaturated polyesters which may be employed in thepractice of the present invention, the alcohol component may compriseethylene glycol, diethylene glycol or propylene glycol, or one of thegroup of solid polyethylene glycols designated as Carbowax.

Polyethylene glycols such as the Carbowaxes are understood to havemolecular weights above 300. Those most useful for this invention haveweights below 4000 and preferably are in a range of about 1000 to 2000,e.g., 1500.

The acid component usually comprises an alpha, betaethylenicallyunsaturated polycarboxylic acid such as maleic, fumaric or itaconicacid, or the well-known derivatives of these polycarboxylic acids havingethylenic unsaturation in alpha-beta relation to the carboxyl group.Polybasic acids such as aconitric acid, tricarballylic acid or citricand may also be employed. A plurality of such acids also may be mixedwith each other, if so desired. In many instances, it may be desirableto include a dicarboxylic acid free of ethylenic unsaturation. Examplesof this latter type of dicarboxylic acid include phthalic acid orterephthalic acid, which, although they contain double bonds in thebenzene ring, do not undergo addition reaction with monomer compoundsand may, therefore, be considered as being the equivalent of saturatedcompounds. Likewise, aliphatic dicarboxylic acids such as succinic acid,adipic acid, sebacic acid, or azelaic acid may be substituted for a partof the alpha, beta-ethylenically unsaturated dicarboxylic acid. Theproportion of the non-ethylene acid with respect to thealpha,betaethylenically unsaturated acid is susceptible of widevariation. A molecular proportion of 0.25 to 12 moles of saturated acidper mole of unsaturated acid is usually used for commercialapplications. Also acid anhydrides of these dicarboxylic acids can beused instead of the di carboxylic acids.

In preparing the polyester, a small excess (usually 5 or 10 percent) ofthe dihydric alcohol is usually employed. The conditions of theesterification reaction are those conventionally employed in preparingpolyesters. For example, the mixture of the alcohol and the acid isheated in a vented container or under an inert atmosphere until thewater of reaction is expelled from the system, which usually occurs in atemperature range of about to 210 C. The reaction is continued until theacid value is reduced to a reasonable low point, e.g., Within a range ofabout 5 to 50, or until the mixture becomes highly viscous or even solidwhen it is cooled. Usually these conditions are attained in a period of2 to hours. In an event, the reaction is concluded before the productbecomes infusible and insoluble because of the advanced stage ofpolymerization. The product is then blended with the ethylenicallyunsaturated monomer in such a manner as to maintain the temperature ofthe blend below 150 F.

The ethylenically unsaturated monomers may be selected from thefollowing general list:

(1) Monoolefinic hydrocarbons, that is, monomers containing only atomsof hydrogen and carbon, such as 1 styrene, alpha-methyl styrene,alpha-ethyl styrene, alphabutyl styrene, vinyl toluene, and the like;

(2) Halogenated monoolefinic hydrocarbons, that is, monomers containingcarbon hydrogen and one or more halogen atoms such asalpha-chlorostyrene, alpha-bromostyrene, 2,5-dichlorostyrene,2,5-dibromostyrene, 3,4-dichlorostyrene, 3,4-difluorostyrene, ortho-,meta and para fiuorostyrenes, 2,6 dichlorostyrene, 2,6 difluorostyrene,3-fluoro-4-chlorostyrene, 2,4,5-trichlorostyrene,dichloromonofluorostyrenes, chloroethylene (vinyl chloride),1,1-dichloroethylene (vinylidene chloride), bromoethylene,fluorethylene, iodoethylene, 1,1-dibromoethylene, 1,1-difluoroethyleue,1,1-diiodoethylene, and the like.

(3) Esters of organic and inorganic acids such as vinyl acetate, vinylpropionate, vinyl butyrate, vinyl isobutyrate, vinyl avalerate, vinylcaproate, vinyl enanthate, vinyl benzoate, vinyl toluate, vinylp-chlorobenzoate, vinyl o-chlorobenzoate, vinyl m-chlorobenzoate andsimilar vinyl halobenzoates, vinyl p-methoxybenzoate, vinylomethoxybenzoate, vinyl p-ethoxybenzoate, methyl methacrylate, ethylmethacrylate, propyl methacrylate, butyl methacrylate, amylmethacrylate, hexyl methacrylate, heptyl methacrylate, octylmethacrylate, decyl methacrylate, methyl crotonate, ethyl crotonate andethyl tiglate, methyl acrylate, ethyl acrylate, propyl acrylate,isopropyl acrylate, butyl acrylate, isobutyl' acrylate, amyl acrylate,hexyl acrylate, 2-ethylhexyl acrylate, heptyl acrylate, octyl acrylate,3,5,5-trimethy1hexyl acrylate, decyl acrylate, and dodecyl acrylate,isopropenyl acetate, isopropenyl propionate, isopropenyl butyrate,isopropenyl valerate, isopropenyl caproate, isopropenyl enanthate,isopropenyl benzoate, isopropenyl p-chlorobenzoate, isopropenylo-bromobenzoate, isopropenyl m-chlorobenzoate, isopropenyl toluene,isopropenyl alpha-chloracetate and isopropenyl alpha-bromopropionate;

Vinyl alpha-chloroacetate, vinyl alpha-bromoacetate, vinylalpha-chloropropionate, vinyl alpha-bromopropionate, vinylalpha-iodopropionate, vinyl alpha-chlorobutyrate, vinylalpha-chlorovalerate and vinyl alphabromovalerate;

Allyl chlorocarbonate, allyl formate, allyl acetate, allyl propionate,allyl butyrate, allyl valerated, al yl caproate, diallyl phthalate,diallyl succinate, diethylene glycol bis (allyl-carbonate), allyl3,5,5-trimethylhexoate, allyl benzoate, allyl acrylate, allyl crotonate,allyl oleate, allyl chloroacetate, allyl trichloroacetate, allylchloropropionate, allyl chlorovalerate, allyl lactate, allyl pyruvate,allyl aminoacetate, allyl aminoacetate, allyl acetoacetate, allylthioacetate, diallyl 3,4,5,6,7,7-hexachloro-4-endomethylenetetrahydrophthalate, as well as methallyl esters corresponding to theabove allyl esters, as well as esters from such alkenyl alcohols asbeta-ethyl allyl alcohol, betapropyl allyl alcohol, 1-buten-4-ol,2-methyl-buten-l-ol-4, 2(2,2-dimethylopropyl)-l-buten-4-ol and l-pentene4-ol;

Methyl alpha-chloroacrylate, methyl alpha-bromoacrylate, methylalpha-fiuoroacrylate, methyl alphaiodoacrylate, ethylalpha-chloroacrylate, propyl alpha-chloroacrylate, isopropylalpha-bromoacrylate, amyl alphachloroacrylate, octylalphachloroacrylate, 3,5,5-trimethylhexyl alpha-chloroacrylate, decylalpha-chloroacrylate, methyl alpha-cyano acrylate, ethyl alpha-cyanoacrylate, amyl alpha-cyano acrylate, amyl alpha-cyano acrylate and decylalpha-cyano acrylate;

Dimethyl maleate, diethyl maleate, diallyl maleate, dimethyl fumarate,dimethallyl fumarate and diethyl glutaconate;

(4) Organic nitriles such as acrylonitrile, methacrylonitrile,ethacrylonitrile, crotonitrile, and the like;

(5) Acid monomers such as acrylic acid, methacrylic acid, crotonic acid,3-butenoic acid, angelic acid, tiglic acid and the like;

(6) Amides such as acrylamide, alphamethyl acrylamide N-phenylacrylamide, N-methyl-N-phenyl acrylamide, N-methyl acrylamide, and thelike.

The preferred monomers are liquid compounds soluble in the polyestercomponent. They will contain the C=CH group and preferably the latterwill be attached to a negative radical such as a benzene ring, achlorine atom, an ester linkage, a nitrile group or the like. Theyshould be free of carbon-carbon conjugated double bonds.

The most preferred polyesters are the burn-resistant type whereinhalogenated aromatic acid anhydrides or halogenatedendomethylenecyclohexane dicarboxylic anhydrides are added as part ofthe dibasic acid moiety. See Examples 1 through 5 for this type ofpolyester resin compositions. The cobalt salt promoter can be placed inthe polyester resin composition during storage or just before curing.

These polyesters are burn resistant by reason of the fact thathalogenated components are present so that the total chlorine content isin the range of to percent by weight or the bromine content is about 10weight percent. The polyesters are either commercial or developmentalpolyesters and are prepared by esterifying mixtures of dibasic acidsand/or anhydrides with a difunctional glycol. Part of the acid moietiesare unsaturated, and the final polyester is diluted with styrene. Theresin for end-use applications is cured with a peroxide catalyst todevelop the final cross-linked three-dimensional thermoset product. Theesterification process in which those resins are produced, isrepresented by the following equation:

0 II C mH0A-OH 2mR O wherein: A is a divalent organic moiety, e.g.,alkylene, aralkylene, cycloalkylene, polyalkylene ether, and the like;-IR is arylene, alkylene, alkenylene, alkarylene, aralkylene and thelike (e.g., phenylene, ethylene, ethenylene, methyl phenylene,phenylethylene, etc); and m is 2 to 10.

In general, monomer component or components may be employed over arelatively broad range, but, usually, the amount thereof upon a weightbasis will be less than that of the polyester component. Usually, thepercentage of monomer will fall within a range of about 10 to 45 percentby weight of the total mixture of polyester and monomer. The preferredrange of monomer is about 20 to percent, in most instances.

The curing time of the polyester resin systems varies between about 1minute and about 24 hours. This time span depends, in part, upon thetype of polyester resin, the amount of catalyst, the amount ofinhibitor, and so forth. The curing temperature of the polyester resinsystems varies between about 15 C. and about 250 C. Preferably, thepolyester resin system can be cured at room temperature (15 to 30 Q).

As the scope of useful polyester resin systems is extensive, the type ofpromoter which can be used in those systems is also extensive. A fewexemplary promoters are given in the following paragraphs.

One of the promoter types which can be used in the polyester resinsystems is a cobalt salt which is capable of being dissolved in theresinous composition. Suitable soluble cobalt octoate or any otherhigher fatty acid salt of cobalt. The amount of cobalt salt can bevaried from about 0.001 to 0.3 percent of the salt calculated asdissolved metallic cobalt based on the total weight of the resincomponents, catalysts and promoter mixture employed. On the same basis,the preferred amount of cobalt metal ranges from about 0.05 to 0.15percent.

The vanadium promoters disclosed in US. Pat. No. 3,333,021 are useful.

Another promoter type material is a variety of amine promoters. Suitableamine promoters are disclosed in U.S. Pat. No. 2,480,928. The promotersare described therein as tertiary monoamines which contain attached tothe nitrogen atom two functionally aliphatic radicals selected from thegroup consisting of alkyl hydrocarbons, hydroxysubstituted alkylhydrocarbons and aralkyl hydrocarbons and one aromatic radical selectedfrom the group consisting of aryl hydrocarbons, azo-substituted arylhydrocarbons, amino-substituted aryl hydrocarbons, andaldehydesubstituted aryl hydrocarbons, and salts thereof. Specificexamples of this class are the following: dimethylaniline,diethylaniline, di-n-propyaniline, dimethyl-p-toluidinedimethyl-o-toluidine, dimethyl-alphanaphthylamine, methyl benzylaniline, p dimethylaminoazobenzene, N,N dimethyl-m-aminophenol,p-dimethylaminophenyl oxalate, p dimethylaminobenzaldehyde, pdimethylaminophenyl acetate, and p-hydroxy-N,N-di(betahydroxyethyl)aniline. Additionally, the promoter can be a tertiary alkylamine, a hydroxy alkyl amine or an acid salt thereof as a promoter.Exemplary of these types of promoters are diethylmethylolamine,triethylamine, triisopropylamine, trimethylamine, tri-isopropanolamine,ethyl diethanolamine hydrochloride and the like. Tertiary polyamines arealso effective for use in the instant manner, such as for example,tetramethylbutanediamine. The amount of amine promoter useful in thepractice of this invention varies between about 0.05 to 1.0 percentbased on the resin components, catalyst and promoter. These aminepromoters can be used in conjunction with the above cobalt promoters.

The polyester resin systems of this invention can also contain othercompatible additives, such as fillers (silica, carbon black), etc.,dyes, reinforcing materials (asbestos, chopped glass fibers), etc.

The resin systems stabilized with agents of this invention are readilycurable, for example, when excess peroxide catalysts and cobalt promoterare employed to destroy, neutralize, or inactivate the inhibitors. Thepreferred catalysts are disclosed in copending application Ser. No.782,734 (Disclosure No. 2,693), filed Dec. 10, 1968, inventors: D. A.Daniels, R. L. Orem and E. W. Lard. For example, the preferred catalystsfor curing the resin systems include a ketone peroxide, such as,Lupersol 224, Lupersol DDM, and an organic non-ketonic diperoxide, suchas Lupersol 256 [which is 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane]. The amount of each preferred catalystcomponent must be based on the amount of each stabilizer present. Ingeneral, the non-ketonic diperoxide can be present in an amount betweenabout 2 to about 3 percent by weight based upon the amount of resincomponents (monomers, etc.) present and the ketone peroxide can bepresent in an amount between about 2 to about 6 percent by weight basedupon the amount of resin components (monomers, etc.) present. The amountof cobalt promoter present can be between about 0.2 to about 0.4 molepercent based upon the amount of resin components (monomers, etc.)present.

To add structural body to the cured polymer resins, materials, such as,styrene, vinyl toluene, u-methylstyrene, dimethylstyrene, themethyl-a-methylstyrenes, u-bromostyrene, fibIOIllOSlYICIlC,a-chlorostyrene, fl-chlorostyrene, diallylphthalate, vinyl acetate,methyl methacrylate and divinylbenzene, can be added to the uncuredpolymer resins so that they can be copolymerized with the other monomercomponents.

Polyester composition A was prepared by admixing and heating (ashereinbefore described) 10 moles of diethylene glycol, 4 moles of maleicanhydride, 5 moles of chlorendic anhydride, 1 mole of adipic acid, 10moles of styrene, and about 0.02 mole of cobalt octoate. There was atotal halogen content of about 25 percent.

EXAMPLE 2 Polyester composition B was prepared by admixing and heating(as hereinbefore described) 10 moles of diethylene glycol, 5 moles ofmaleic anhydride, 5 moles of chlorendic anhydride, and 10 moles ofstyrene. There was a total halogen content of about 25 percent. (Acobalt compound, or other catalyst, must be placed in the com positionbefore it can be cured after storage.)

EXAMPLE 3 Polyester composition C was prepared by admixing and heating(as hereinbefore described) 10 moles of diethylene glycol, 5 moles ofmaleic anhydride, 5 moles of chlorendic anhydride, 10 moles of styrene,and about 0.02 mole of cobalt octoate. There was a total halogen contentof about 25 percent.

EXAMPLE 4 Polyester composition D was prepared by admixing and heating(as hereinbefore described) 10 moles of diethylene glycol, 6.2 moles ofmaleic anhydride, 1.2 moles of tetrabromophthalic anhydride, 2.6 molesof phthalic anhydride and 10 moles of styrene. There was a total halogencontent of about 9 to about 11 percent. (A cobalt compound, or othercatalyst, must b placed in the composition before it can be cured afterstorage.)

EXAMPLE 5 Polyester composition E was prepared by admixing and heating(as hereinbefore described) 10 moles of diethylene glycol, 6.2 moles ofmaleic anhydride, 1.2 moles of tetrabromophthalie anhydride, 2.6 molesof phthalic anhydride, 10 moles of styrene, and about 0.02 mole ofcobalt octoate. There was a total halogen content of about 9 to about 11percent.

EXAMPLE 6 2,3-dihydroxypyridine (1.0 mole percent) was admixed withpolyester C, and the admixture was stored (immediately afterpreparation) at a temperature of 70 C. The gel time for the compositionwas :1 days.

EXAMPLE 7 2,3-dihydroxypyridine (1.0 mole percent) was admixed withpolyester C, and the admixture was stored (immediately afterpreparation) at a temperature of 25 C. The gel time for the compositionwas 8000:200 days. (This is an extrapolated value which was obtained bythe extrapolation technique given above.)

EXAMPLE 8 Polyester A was stored (immediately after preparation) at atemperature of 70 C. The gel time for the composition was 11:0.5 days.

9 EXAMPLE 9 Polyester A was stored with 0.001 weight percent hydroquinone at a temperature of 25 C. The gel time for the compositionwas 200:50 days. (This is an extrapolated value which was obtained bythe extrapolation technique given above.)

EXAMPLE 10 2-hydroxypyridine (1.0 mole percent) was admixed withpolyester A, and the admixture was stored (immediately afterpreparation) at a temperature of 70 C. The gel time for the compositionwas 40:10 days.

EXAMPLE 11 EXAMPLE 12 Polyester D was stored (immediately afterpreparation) at a temperature of 70 C. The gel time for the compositionwas 9:0.5 days.

EXAMPLE 13 Polyester D was stored (immediately after preparation) at atemperature of C. The gel time for the composition was 750:50 days.(This is an extrapolated value which was obtained by the extrapolationtechnique given above.)

EXAMPLE 14 2-hydroxypyridine (1.0 mole percent) was admixed withpolyester D, and the admixture was stored (immediately afterpreparation) at a temperature of 70 C. The gel time for the compositionwas :10 days.

EXAMPLE 15 2-hydroxypyridine (1.0 mole percent) was admixed withpolyester D, and the admixture was stored (immediately afterpreparation) at a temperature of 25 C. The gel time for the compositionwas 3000:200 days. (This is an extrapolated value which was obtained bythe extrapolation techniqu given above.)

EXAMPLE 16 3-hydroxypyridine (1.0 mole percent) was admixed withpolyester B, and the admixture was stored (immediately afterpreparation) at a temperature of 70 C. The gel time for the compositionwas :5 days.

EXAMPLE l7 4-hydroxypyridine (0.05 mole percent) was admixed withpolyester E, and the admixture was stored (immediately afterpreparation) at a temperature of 70 C. The gel time for the compositionwas 30:5 days.

EXAMPLE 18 2,4-dihydroxypyridine (1.0 mole percent) was admixed withpolyester B, and the admixture was stored (immediately afterpreparation) at a temperature of 70 C. The gel time for the compositionwas :2 days.

EXAMPLE 19 2,5-dihydroxypyridine (0.5 mole percent) was admixed withpolyester B, and the admixture was stored (immediately afterpreparation) at a temperature of 70 C. The gel time for the compositionwas 33 :3 days.

EXAMPLE 20 2-hydroxypyridine (0.2 mole percent) was admixed Withpolyester B, and the admixture was stored (immediately afterpreparation) at a temperature of 125 C. The gel time for the compositionwas 0.4:0.0S day.

EXAMPLE 21 An uncured polyester resin system containing 3.7 Weightpercent Lupersol 224, 2.7 weight percent Lupersol 256, and 93.6 weightpercent polyester composition (including styrene and inhibitor) similarto the one of Example 17. Lupersol 224 is a trade designation for asolution of 3,5-dimethyl-3,S-dihydroxy-1,2-peroxycyclopentane (30percent purity), having an active oxygen content of 4.0 percent, whichis commercially available.

The polyester resin system containing the catalysts and promoters wascured by heating the system between 77 and F. for 25 minutes. The curingis an exothermic autoaccelerative reaction. The resin system gelledafter 20 minutes and the peak temperature was 250 F. A well-curedpolyester resin was obtained. After 24 hour-s, the flexural modulus was220,000 p.s.i.

EXAMPLE 22 Example 21 was repeated, except that the polyestercomposition (including the inhibitor) was similar to the one of Example14. 0.002 mole percent of cobalt octoate was added before curing. AWell-cured polyester resin was obtained.

EXAMPLE 23 2,3-dihydroxypyridine (0.5 mole percent) and2-hydroxypyridine (0.5 mole percent) were admixed with polyester B, andthe admixture was stored (immediately after preparation) at atemperature of 70 C. The gel time for the composition was 55:5 days.

EXAMPLE 24 An uncured polyester resin system containing 18.1 Weightpercent fiber glass (three layers of glass fabric), 1.5 weight percentcobalt octoate solution (12 percent cobalt), 3.7 weight percent3,5-dimethyl-3,S-dihydroxy- 1,2-peroxycyclopentane solution (30 partsdissolved in 70 parts of propylene glycol), 2.7 weight percent Lupersol256, and 74.0 weight percent of the polyester resin components(including styrene) of Example 21. The uncured polyester resin systemalso contained 1.0 mole percent 2-hydroxypyridine (inhibit-or). Thepolyester was then cured as in Example 21.

EXAMPLE 25 Example 24 was repeated, except that the solvent in the1,2-peroxycyclopentane solution was hexylene glycol. A well-cured resinwas obtained.

EXAMPLE 26 Example 24 was repeated, except that the solvent in the1,2-peroxycyclopentane solution was a 50/50 mixture of water andhexylene glycol. A well-cured resin was obtained.

EXAMPLE 27 Example 26 was repeated, except that the1,2-peroxycyclopentane was replaced with:

A well-cured resin was obtained after 24 hours having a flexural modulusof 500,000 p.s.i.

EXAMPLE 28 Example 14 was repeated, except that polyester resin Dcontained propylene glycol instead of diethylene glycol. The gel timefor the composition was 40:10 days (storage temperature was 70 C.).

EXAMPLE 29 Toluhydroquinone (1.2 mole percent) was admixed withpolyester C, and the admixture was stored (immediately afterpreparation) at a temperature of 70 C. The gel time for the compositionwas 41:1 days.

EXAMPLE 30 Toluhydroquinone (1.2 mole percent) was admixed withpolyester A, and the admixture was stored (immediately afterpreparation) at a temperature of 70 C. The gel time for the compositionwas 30:1 days.

Lupersol DDM is a solution comprising 60% methyl ethyl ketone peroxidesand hydroperoxides in dimethyl phthalate. Lupersol 224 is a solutioncomprising 30% 3,5-dimethyl-3,S-dihydroxy-l,2-peroxycyclopentane intriethyl phosphate. Luper-sol 256 is a difunctional polyester catalystdesigned especially for elevated temperature applications comprising atleast 90% 2,5-dimethyl-2,5-bis (2-ethyl hexanoylperoxy)hexane and havingat least 6.69% available oxygen.

EXAMPLE 3 1 Example 24 was repeated, except that the1,2-peroxycyclopentane solution was comprised of 30 percent 3,5-dimethyl-3,5-dihydroxy-1,2-peroxycyclopentane, 12 percent water, 29percent triethyl phosphate and 29 percent N-alkyl-Z-pyrrolidinone. Awell-cured resin was obtained.

It is claimed:

1. A stabilized uncured burn resistant polyester resin compositionconsisting essentially of:

(a) an unsaturated polyester of: (i) a polyhydric alcohol selected froma first group consisting of ethylene glycol, diethylene glycol,propylene glycol and a polyethylene glycol having a molecular weightbetween 300 and 4000; (ii) a member selected from a second groupconsisting of chlorendic acid and chlorendic anhydride; (iii) a memberselected from a third group consisting of maleic acid, fumaric acid,itaconic acid, and aconitic acid or an anhydride of the third groupmember; and (iv) a member selected from a fourth group consisting oftricarballyic acid, citric acid, succinic acid, adipic acid, sebacicacid, azelaic acid, phthalic acid, and terephthalic acid or an anhydrideof the fourth group member, the chlorine content of the stabilizedpolyester resin composition being 25 to 30%, the mole ratio of the thirdgroup member to the fourth group member being 1:0.25-12;

(b) an ethylenically unsaturated monomer selected from a fifth groupconsisting of styrene, vinyl toluene, a-methylstyrene, dimethylstyrene,the methyl-u-methylstyrenes, ot-bromostyrene, B-bromostyrene, u-ChlOlO-styrene, ,B-chlorostyrene, diallylphthalate, vinyl acetate, methylmethaciylate, and divinylbenzene, the fifth group member constitutingabout 45% of the polyester resin composition; and

(c) an inhibitor having the formula where R is H or OH; R is H or OH; Ris -H or OH; R; is H or OH; and R is H or OH; provided at least one of RR R R and R is OH, the inhibitor being present in an amount betweenabout 0.05 and about 1.0 mole percent, based on the fifth group memberpresent in the polyester resin composition. 2. The composition of claim1 in which the fifth group member is styrene.

3. The composition of claim 1 in which the fifth group memberconstitutes 20-40% of the polyester resin composition.

4. The composition of claim 1 in which the inhibitor is2-hydroxypyridine.

5. The composition of claim 1 in which the inhibitor is2,3-dihydroxypyridine.

6. A stabilized uncured burn resistant polyester resin compositionconsisting essentially of:

(a) an unsaturated polyester of: (i) a polyhydric alcohol selected froma first group consisting of ethylene glycol, diethylene glycol,propylene glycol, and a polyethylene glycol having a molecular weightbetween 300 and 4000; (ii) a member selected from a second groupconsisting of tetrabromophthalic acid and tetrabromophthalic anhydride;(iii) a member selected from a third group consisting of maleic acid,fumaric acid, itaconic acid, and aconitic acid or an anhydride of thethird group member; and (iv) a member selected from a fourth groupconsisting of tricarballyic acid, citric acid, succinic acid, adipicacid, sebacis acid, azelaic acid, phthalic acid, and terephthalic acidor an anhydride of the fourth group member, the bromine content of saidcomposition being about 10%, the mole ratio of the third group member tothe fourth group member being 1:0.25-12;

(b) an ethylenically unsaturated monomer selected from a fifth groupconsisting of styrene, vinyl toluene, a-methylstyrene, dimethylstyrene,the methyl-a-methylstyrene, a-bromostyrene, fi-bromostyrene,a-chlorostyrene, B-chlorostyrene, diallylphthalate, vinyl acetate,methyl methacrylate, and divinylbenzene, the fifth group memberconstituting about 1045% of the polyester resin composition; and

(c) an inhibitor having the formula where R is H or OH; R is --H or OH;R is H or OH; R; is H or OH; and R is H or OH; provided at least one ofthe R R R R and R is OH, the inhibitor being present in an amountbetween about 0.04 and about 1.0 mole percent based on the fifth groupmember present in the polyester resin composition.

7. The composition of claim 6 in which the fifth group member isstyrene.

8. The composition of claim 6 in which the fifth group memberconstitutes 2040% of the polyester resin composition.

9. The composition of claim 6 in which the inhibitor is2-hydroxypyridine,

10. The composition of claim 6 in which the inhibitor is2,3-dihydroxypyridine.

References Cited UNITED STATES PATENTS 2,610,168 9/1952 Anderson 260-8642,779,701 1/1957 Robitschek et al 154-43 3,377,407 4/1968 Kressin et al260863 OTHER REFERENCES Lawrence, Polyester Resins, 1960, pp. 3032.

WILLIAM SHORT, Primary Examiner R. J. KOCH, Assistant Examiner US. Cl.X,R.

